Shape memory polymer actuator and catheter

ABSTRACT

An actuator system is provided for acting upon a material in a vessel. The system includes an optical fiber and a shape memory polymer material operatively connected to the optical fiber. The shape memory polymer material is adapted to move from a first shape for moving through said vessel to a second shape where it can act upon said material.

REFERENCE TO PROVISIONAL APPLICATION TO CLAIM PRIORITY

[0001] This application claims the benefit under 35 U.S.C. § 119(e) ofU.S. provisional patent application No. 60/246,293, filed Nov. 6, 2000,which is hereby incorporated by reference in its entirety.

CROSS-REFERENCE TO RELATED APPLICATION

[0002] This application is a division of application Ser. No. 09/761,023entitled “Shape Memory Polymer Actuator and Catheter,” filed Jan. 16,2001.

[0003] The United States Government has rights in this inventionpursuant to Contract No. W-7405-ENG-48 between the United StatesDepartment of Energy and the University of California for the operationof Lawrence Livermore National Laboratory.

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] The present invention relates to actuators and in particular to ashape memory polymer actuator.

[0006] 2. State of Technology

[0007] U.S. Pat. No. 5,836,868 for an expandable intravascular occlusionmaterial removal devices and methods of use, by Ressemann et al,patented Nov. 17, 1998, provides the following description: “The presentinvention generally relates to constructions for intravascular treatmentdevices useful for removing vascular occlusion material from a vascularocclusion or from a vascular lumen. The invention more specificallyrelates to expandable intravascular occlusion material removal devices,as well as to methods of using those devices to treat vascular diseases.

[0008] Vascular diseases, such as atherosclerosis and the like, havebecome quite prevalent in the modern day. These diseases may presentthemselves in a number of forms. Each form of vascular disease mayrequire a different method of treatment to reduce or cure the harmfuleffects of the disease. Vascular diseases, for example, may take theform of deposits or growths in a patient's vasculature which mayrestrict, in the case of a partial occlusion, or stop, in the case of atotal occlusion, blood flow to a certain portion of the patient's body.This can be particularly serious if, for example, such an occlusionoccurs in a portion of the vasculature that supplies vital organs withblood or other necessary fluids.

[0009] To treat these diseases, a number of different therapies arebeing developed. While a number of invasive therapies are available, itis desirable to develop non-invasive therapies as well. Non-invasivetherapies may be less risky than invasive ones, and may be more welcomedby the patient because of the possibility of decreased chances ofinfection, reduced post-operative pain, and less post-operativerehabilitation. One type of non-invasive therapy for vascular diseasesis pharmaceutical in nature. Clot-busting drugs have been employed tohelp break up blood clots which may be blocking a particular vascularlumen. Other drug therapies are also available. Further non-invasive,intravascular treatments exist that are not only pharmaceutical, butalso revascularize blood vessels or lumens by mechanical means. Twoexamples of such intravascular therapies are balloon angioplasty andatherectomy which physically revascularize a portion of a patient'svasculature.

[0010] Balloon angioplasty comprises a procedure wherein a ballooncatheter is inserted intravascularly into a patient through a relativelysmall puncture, which may be located proximate the groin, andintravascularly navigated by a treating physician to the occludedvascular site. The balloon catheter includes a balloon or dilatingmember which is placed adjacent the vascular occlusion and then isinflated. Intravascular inflation of the dilating member by sufficientpressures, on the order of 5 to 12 atmospheres or so, causes the balloonto displace the occluding matter to revascularize the occluded lumen andthereby restore substantially normal blood flow through therevascularized portion of the vasculature. It is to be noted, however,that this procedure does not remove the occluding matter from thepatient's vasculature, but displaces it.

[0011] While balloon angioplasty is quite successful in substantiallyrevascularizing many vascular lumens by reforming the occludingmaterial, other occlusions may be difficult to treat with angioplasty.Specifically, some intravascular occlusions may be composed of anirregular, loose or heavily calcified material which may extendrelatively far along a vessel or may extend adjacent a side branchingvessel, and thus are not prone or susceptible to angioplastic treatment.Even if angioplasty is successful, thereby revascularizing the vesseland substantially restoring normal blood flow therethrough, there is achance that the occlusion may recur. Recurrence of an occlusion mayrequire repeated or alternative treatments given at the sameintravascular site.

[0012] Accordingly, attempts have been made to develop other alternativemechanical methods of non-invasive, intravascular treatment in an effortto provide another way of revascularizing an occluded vessel and ofrestoring blood flow through the relevant vasculature. These alternativetreatments may have particular utility with certain vascular occlusions,or may provide added benefits to a patient when combined with balloonangioplasty and/or drug therapies.

[0013] One such alternative mechanical treatment method involvesremoval, not displacement, as is the case with balloon angioplasty, ofthe material occluding a vascular lumen. Such treatment devices,sometimes referred to as atherectomy devices, use a variety of means,such as lasers, and rotating cutters or ablaters, for example, to removethe occluding material. The rotating cutters may be particularly usefulin removing certain vascular occlusions. Since vascular occlusions mayhave different compositions and morphology or shape, a given removal orcutting element may not be suitable for removal of a certain occlusion.Alternatively, if a patient has multiple occlusions in his vasculature,a given removal element may be suitable for removing only one of theocclusions. Suitability of a particular cutting element may bedetermined by, for example, its size or shape. Thus, a treatingphysician may have to use a plurality of different treatment devices toprovide the patient with complete treatment. This type of procedure canbe quite expensive because multiple pieces of equipment may need to beused (such intravascular devices are not reusable because they areinserted directly into the blood stream), and may be tedious to performbecause multiple pieces of equipment must be navigated through anoften-tortuous vascular path to the treatment site.”

[0014] U.S. Pat. No. 5,102,415, for an apparatus for removing bloodclots from arteries and veins, by Guenther et al, patented Apr. 7, 1992,provides the folowing description: “A triple catheter for removing ofblood clots from arteries and veins is equipped with an outer catheterthat can be inserted into a blood vessel and an inner catheter with aninflatable baloon at its distal end that can be inserted into the outercatheter. The inner catheter is surrounded by an intermediate catheteralso inserted into the outer catheter. The intermediate catheter has aradially expandable distal end receptacle made of an elastic meshstructure of spring wires or plastic monofilaments covered by orembedded in an elastic plastic coating. A very small puncture channel isrequired for the insertion of such a triple catheter through the wall ofa blood vessel.”

[0015] U.S. Pat. No. 5,645,564 for microfabricated therapeutic actuatormechanisms, by Northrup et al, patented Jul. 8, 1997, provides thefolowing description: “Electromechanical microstructures(microgrippers), either integrated circuit (IC) silicon-based orprecision machined, to extend and improve the application ofcatheter-based interventional therapies for the repair of aneurysms inthe brain or other interventional clinical therapies. Thesemicromechanisms can be specifically applied to release platinum coils orother materials into bulging portions of the blood vessels also known asaneurysms. The “micro” size of the release mechanism is necessary sincethe brain vessels are the smallest in the body. Through a catheter morethan one meter long, the micromechanism located at one end of thecatheter can be manipulated from the other end thereof. The microgripper(micromechanism) of the invention will also find applications innon-medical areas where a remotely actuated microgripper or similaractuator would be useful or where micro-assembling is needed.”

[0016] U.S. Pat. No. 6,102,917 for a shape memory polymer (SMP) gripperwith a release sensing system, by Maitland et al, patented Aug. 15,2000, provides the following description: “A system for releasing atarget material, such as an embolic coil from an SMP located at the endof a catheter utilizing an optical arrangement for releasing thematerial. The system includes a laser, laser driver, display panel,photodetector, fiber optics coupler, fiber optics and connectors, acatheter, and an SMP-based gripper, and includes a release sensing andfeedback arrangement. The SMP-based gripper is heated via laser lightthrough an optic fiber causing the gripper to release a target material(e.g., embolic coil for therapeutic treatment of aneurysms). Variousembodiments are provided for coupling the laser light into the SMP,which includes specific positioning of the coils, removal of the fibercladding adjacent the coil, a metal coating on the SMP, doping the SMPwith a gradient absorbing dye, tapering the fiber optic end, coating theSMP with low refractive index material, and locating an insert betweenthe fiber optic and the coil.”

[0017] U.S. Pat. No. 5,843,118 for fibered micro vaso-occlusive devices,by Sepetka et al, patented Dec. 1, 1998, provides the followingdescription: “This is a vaso-occlusive device made up of at least oneshort retainer and a longer fiber bundle. The retainer may beradio-opaque. The fibers may be straight, looped, or tufted. The primaryuse of the device is in the very small vessels at the distal portion ofthe vasculature.”

[0018] U.S. Pat. No. 5,895,398 for a method of using a clot capturecoil, by Wensel et al, patented Apr. 20, 1999, provides the followingdescription: “A clot and foreign body removal device is described whichcomprises a catheter with at least one lumen. Located within thecatheter is a clot capture coil that is connected to an insertionmandrel. In one embodiment, the clot capture coil is made out of a solidelastic or superelastic material which has shape memory, preferablynitinol. The elasticity or superelasticity of the coil allows it to bedeformed within the catheter and to then reform its original coilconfiguration when the coil is moved outside of the catheter lumen. Inanother embodiment the coil is a biphasic coil which changes shape uponheating or passing an electric current. Once the coil configuration hasbeen established, the coil can be used to ensnare and corkscrew a clotin a vessel. A clot is extracted from the vessel by moving the clotcapture coil and catheter proximally until the clot can be removed orreleased into a different vessel that does not perfuse a critical organ.Foreign bodies are similarly captured by deploying the coil distal tothe foreign body and moving the clot capture coil proximally until theforeign body is trapped within the coil. By removing the device from thebody, the foreign material is also removed.”

SUMMARY OF THE INVENTION

[0019] The present invention provides an actuator system. The systemuses heat to activate a shape memory material. The shape memory materialwill change shape when heated above a transition temperature. The shapememory material is adapted to move from a first shape to a second shapewhere it can perform a desired function. In one embodiment of thepresent invention a method of removing matter from a vessel isdescribed. A catheter with a shape memory material is transported to thesite of the matter to be removed. The shape memory material is passedthrough or around the matter. Heat is utilized to activate the shapememory material and expand the shape memory material. By withdrawing thecatheter and the shape memory material through said vessel the matter iscarried from the vessel. Additional aspects, advantages, and features ofthe invention are set forth in part in the following description.Various aspects, advantages, and features of the invention will becomeapparent to those skilled in the art upon examination of the descriptionand by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated into and form apart of the disclosure, illustrate embodiments of the invention, and,together with the description, serve to explain the principles of theinvention.

[0021]FIG. 1 is a conceptual illustration of an embodiment of thepresent invention in a vessel with a blockage such as a blood clot.

[0022]FIG. 2 is a conceptual illustration of an embodiment of thepresent in a vessel in an expanded position.

[0023]FIG. 3 is a conceptual illustration showing that when the shapememory material actuator is drawn backward it results in removal of theblockage.

[0024]FIG. 4 shows an embodiment of a shape memory polymer actuator inits loaded state.

[0025]FIG. 5 shows an embodiment of a shape memory polymer actuator inits expanded state.

[0026]FIG. 6 is a schematic illustration showing the cross section of aclosed shape memory polymer actuator.

[0027]FIG. 7 shows the shape memory polymer actuator used in conjunctionwith a guide tube (catheter).

[0028]FIG. 8 shows the shape memory polymer actuator used in conjunctionwith a guide tube (catheter).

[0029]FIG. 9 shows the shape memory polymer actuator used in conjunctionwith a guide tube (catheter).

[0030]FIG. 10 shows the shape memory polymer actuator used inconjunction with a guide tube (catheter).

[0031]FIG. 11 shows an enhancement to the basic design.

[0032]FIG. 12 shows an enhancement to the basic design.

[0033]FIG. 13 shows an enhancement to the basic design.

[0034]FIG. 14 shows an enhancement to the basic design.

[0035]FIGS. 15A, 15B, and 15C illustrate integrating radio-opaquemarkers into the shape memory polymer actuator.

[0036]FIG. 16 illustrates a diagnostic sensor at the distal tip of theshape memory polymer actuator.

[0037]FIG. 17 shows a sensor attached, deposited or embedded in thedistal end of the shape memory polymer actuator.

[0038]FIG. 18 shows light is coupled directly into the shape memorypolymer actuator and aimed at the umbrella section where actuation isrequired.

[0039]FIG. 19 shows use of multiple umbrellas.

[0040]FIG. 20 shows opposing umbrellas used to scrape the walls in bothdirections to contain more of the debris.

[0041]FIG. 21 shows different wavelengths, filters or transitiontemperatures for independent control of two shape memory polymeractuators.

[0042]FIG. 22 shows different wavelengths, filters or transitiontemperatures for independent control of two shape memory polymeractuators.

[0043]FIG. 23 shows end views of two umbrellas illustrating how theteeth along the outer rim of the two umbrellas interlock and provideimproved scraping.

[0044]FIG. 24 shows teeth along the outer rim of an umbrella for easyinterlocking and improved scraping.

[0045]FIG. 25 shows a snap type locking system where the rim of one conesnaps into the rim of the other to enclose the debris through opticalactuation.

[0046]FIG. 26 shows barbs inside and along the rim help to hook and holdthe debris.

[0047]FIG. 27 shows a clamp holding the umbrella closed duringtransport.

[0048]FIG. 28 shows the umbrella opened.

[0049]FIG. 29 shows an undesired effect of tethers.

[0050]FIG. 30 shows an undesired effect of tethers.

[0051]FIG. 31 shows an improvement on tethers.

[0052]FIG. 32 shows independent control of two shape memory polymeractuators.

[0053]FIG. 33 is a conceptual illustration of another embodiment of thepresent invention in a vessel with a blockage such as a blood clot.

DETAILED DESCRIPTION OF THE INVENTION

[0054] Referring now to the drawings, and in particular to FIGS. 1, 2,and 3 of the drawings, a medical application of an embodiment of anactuator constructed in accordance with the present invention isillustrated. Although a specific application of the present invention isdescribed, it is to be understood that the invention is intended to begeneral in nature, and can be employed wherever actuators are needed.The methods and devices are general to all applications of actuation andcontrol of a shaped memory material.

[0055] The present invention provides an actuator system. The systemuses heat to activate a shape memory material. The shape memory materialwill change shape when heated above a transition temperature. The shapememory material is adapted to move from a first position to a secondposition where it can perform a desired function. In this embodiment ofthe present invention a method of removing matter from a vessel isdescribed. A catheter with a shape memory material is transported to thesite of the matter to be removed. The shape memory material is passedthrough or around the matter. Heat is utilized to activate the shapememory material and expand the shape memory material. By withdrawing thecatheter and the shape memory material through said vessel the matter iscarried from the vessel. The present invention can be used to removeblockages from many luminal structures.

[0056] The shape memory material can be heated using various systems.For example, the shape memory material can be heated as described inU.S. Pat. No. 5,911,737 for microfabricated therapeutic actuators, byLee et al, patented Jun. 15, 1999 as follows: “Heating of the SMP tubing20 can be accomplished via induced resistive heating of the end 22 ofobject 21 by an external wave field, such as by an associated magneticor radio frequency (RF) source, provided of cause that the end 22 ofobject 21 is constructed of material inductive of resistance heating.External heating of the end 22 of object 21 can be carried out throughelectrical induction or electrothermal heating (through a dielectriclossy material on the end of the coil). An example is by applying anexternal alternating magnetic field to Ni—Pd material coated on at leastthe end 22 of object or coil 21.” The disclosure of U.S. Pat. No.5,911,737 is incorporated herein by reference. The shape memory materialcan also be heated using an optical system. The system uses energy inthe form of light guided by an optical fiber to a light, diffusingdevice that radiates the light into the shape memory material. The lightis absorbed by the shape memory material and converted into heat.

[0057]FIG. 1 shows a vessel 10 with a blockage 11. The blockage could bea blood clot, plaque, other emboli, or other blockage. A supportstructure 12 with a shape memory material actuator 13 on its distal endis inserted through or around the blockage 11. The shape memory materialactuator 13 is used to remove the blockage 11 from the vascular system.

[0058]FIG. 2 shows the expanded shape memory material actuator 13.Actuation is achieved by heating the shape memory material. The shapememory material can be heated using various systems. These systemsinclude induced resistive heating by an external wave field, such as byan associated magnetic or radio frequency (RF) source, external heatingthrough electrical induction or electrothermal heating, with local orremote ultrasonics or other acoustic means of energy transfer, or byconverting optical energy into thermal energy that allows the storedenergy in the shape memory material to be released. The heating of theSMP can be accomplished by an operatively connected or embeddedmechanism which is powered by the absorption of applied energy in theform of light, electric fields, magnetic fields, RF fields, EM waves,acoustic/ultrasound waves, electric current flow (DC: resistive heating,AC: inductive or dielectric heating), chemical reactions and/or otherheating mechanisms such as nuclear heating ect. The optical energy isabsorbed by the shape memory material and converted into thermal energythat heats the shape memory material above its transition temperatureand the shape memory material moves to its primary shape, resulting inopto-mechanical actuation.

[0059]FIG. 3 shows that, when the shape memory material actuator isdrawn backward it results in the removal of the blockage from the vessel10. The catheter with the shape memory material 13 was transported tothe site of the matter 11 to be removed. The shape memory material 13was passed through or around the matter 11. Heat was utilized toactivate the shape memory material 13 and expand the shape memorymaterial 13. By withdrawing the support structure 12 and the shapememory material 13 through the vessel 10 the matter 11 was carried fromthe vessel 10.

[0060] The shape memory material actuator system has significantutility, for example, the treatment cost of ischemic strokes isestimated to be $20 Billion/year. The support structure 12 shown inFIGS. 1 and 2 uses an expanding opto-mechanical actuator system. Thesystem uses energy in the form of light guided by an optical fiber to alight diffusing device that radiates the light into the shape memorymaterial. The light is absorbed by the shape memory material andconverted into heat. The shape memory material will change shape whenheated above a transition temperature.

[0061] Referring now to FIGS. 4 and 5, a shape memory material,specifically a shape memory polymer (SMP), SMP actuator systemconstructed in accordance with the present invention is schematicallyillustrated. The shape memory polymer (SMP) actuator system isdesignated generally by the reference numeral 14. The system 14 is anopto-mechanical system that, similar to a guide wire that is commonlypushed through the blood clot, is fed through or around the clot andthen actuated to open like an umbrella. The expanded opto-mechanicaldevice is retracted and the blockage is removed. The system includes thefollowing components:

[0062] Optical Fiber 15—The optical fiber 15 is typically sheathed in abuffer jacket 16 with additional material layers built up to form abiocompatible catheter. The fiber is multimode with typical coredimensions between 50-1000 μm. The distal end 17 of the fiber 15delivers light to a diffusing chamber 18.

[0063] Optical Source 15 a—The optical source 15 a provides light energythrough the optical fiber 15. The optical source 15 a can be a lightsource coupled into an optical fiber. The light is radiated from thelight source. The light is transmitted by the optical fiber 15 to thediffusing device. The diffusing device transmits the light to the shapememory material. The optical source 15 a can be various systems. Forexample, the optical source 15 a can be heated as described in U.S. Pat.No. 6,102,917, by Maitland et al, patented Aug. 15, 2000, as follows:“The catheter section 11, extension section 14, and control unit 15 areinterconnected by optic fiber connectors 16 and 17. Control unit 15includes a laser 18, laser control or driving electronics and displaypanel assembly generally indicated at 19, and connected as indicated at20 to laser 18. Laser 18 is connected by optic fibers 21 and 22 via anoptic fiber connector 23 to a fiber optic coupler 24, such as aconventional 90/10 optical coupler, which is connected via an opticfiber 25 to optic fiber connector 17. Coupler 24, wherein 90 percent ofthe light passes through and 10 percent is bypassed, is also connectedby an optic fiber 26 to a sensing photodetector 27, which is connectedto the display panel section of assembly 19 as indicated at 28. Coupler24 is also connected by an optic fiber 29 to a source photodetector 30,which is connected to the driving electronics or control section ofassembly 19, as indicated at 31. Laser light (pulsed or continuous) fromlaser 18 is transmitted, as indicated by pulses and arrows 32, throughoptic fiber 21, connector 23, optic fiber 22, coupler 24, optic fiber25, connector 17, an optic fiber 14′ in extension section 14, connector16, and an optic fiber 11′ in catheter section 11 onto an end section ofSMP microgripper 12, which retains the coil 13, causing heating of thematerial of microgripper 12 located around the coil.” The disclosure ofU.S. Pat. No. 6,102,917 is incorporated herein by reference.

[0064] Diffusing Chamber 18—The diffusing chamber 18 distributes thelight evenly around the circumference of the chamber and along thechamber length. The distal end 19 of the chamber is terminated with areflective coating or plug 20 that maximizes the amount of light in thechamber. Typical lengths of the diffusing chamber are 100-5000 μm. Atranslucent plastic which scatters light is one example of material thatcould be used in the diffusing chamber.

[0065] Shape Memory Polymer (SMP) 21—SMP materials are well known. Forexample, U.S. Pat. No. 6,086,599 for micro devices using shape memorypolymer patches for mated connections, by Lee et al, patented Jul. 11,2000, states: “SMP material is known in the art, and has been recentlyutilized as delivery means for medical or non-medical devices toinaccessible locations, such as blood vessels or inside a machine ortubing system.” U.S. Pat. No. 5,911,737 for microfabricated therapeuticactuators, by Lee et al, patented Jun. 15, 1999 describes a SMP materialas follows: “The SMP material, a polyurethane-based material thatundergoes a phase transformation at a temperature (Tg). The SMP materialcan be constructed so as to be inert to any fluids of the human body,for example, and can be constructed to be responsive to various desiredphase transformation temperatures, Tg, above which the material is softand reshapable and then by cooling the material below the Tg, thematerial retains the reshaped configuration until it is again heated toabove the Tg temperature at which time the SMP material returns to itsoriginal memory shape.” U.S. Pat. No. 6,102,917 for a shape memorypolymer (SMP) gripper with a release sensing system, by Maitland et al,patented Aug. 15, 2000, describes a SMP material as follows: “SMP, apolyurethane-based material that undergoes a phase transformation at atemperature (Tg) of choice.

[0066] After the material is polymerized (cross-linked), the material ismolded into its memory shape. At temperatures above Tg, the material canbe easily reshaped into another configuration, and upon cooling belowthe Tg the new shape is fixed, but upon increasing the temperature toabove the Tg, the material will return to its original memory shape.”U.S. Pat. No. 5,189,110 for a shape memory polymer resin, compositionand the shape memorizing molded product thereof, by Ikematu et al,patented Feb. 23, 1993, provides the following description: “A shapememory polymer resin, consisting essentially of a block copolymer havingan A-B-A block structure in the polymer chain, and having an averagemolecular weight within the range of 10,000 to 1,000,000, wherein (a)block A is a polymer block comprising a homopolymer or a copolymer of avinyl aromatic compound and/or a hydrogenated product thereof; (b) blockB is a polymer block comprising a homopolymer or a copolymer ofbutadiene and/or a hydrogenated product thereof, the content ofbutadiene and/or the hydrogenated product thereof in block B being atleast 80% by weight, and 80 to 91% of the linkages of the butadieneand/or the hydrogenated product thereof being 1,4-linkages; (c) at least80% by weight of the conjugated diene in the block copolymer beinghydrogenated; and (d) the block copolymer comprises 5 to 50% by weightof said block A; and a shape memory resin composition and a shapememorizing molded product thereof.” The patents identified in thisparagraph are incorporated herein by reference.

[0067] The SMP 21 is attached to the outer fiber optic layer at itsdistal end 22. When light from the diffusing chamber 18 is absorbed inthe SMP 21 the polymer is heated and the proximal end relaxes to itsprimary shape. The primary shape of the SMP 21 is formed by heating theSMP 21 above its melting temperature as in an extrusion or moldingprocesses. Typical lengths for the active region of the SMP are 100-5000μm. The typical angle of the expanded SMP is between 0-90 degrees;however the angle could be beyond 90 degrees up to 180 degrees.

[0068] This embodiment focuses on the opto-mechanical methods and designnecessary to develop a shape memory polymer (SMP) actuator 14 capable ofremoving blockages from a lumen. SMP actuation is based on the uniqueproperty of the shape memory polymer. This polymer possesses a glasstransformation temperature (T_(g)) above which the material enters areversible glassy phase where it becomes soft and flexible and easy toreshape the material. Once cooled below T_(g), the shape is frozen inplace and the material becomes hardened to over 200 times the elasticmodulus of the glassy phase. The reshaped SMP can be used to hold itsshape until it is intentionally relaxed by heating the SMP above T_(g)again.

[0069] The system uses energy in the form of light guided by an opticalfiber to a light diffusing device that radiates the light into the shapememory polymer. The light is absorbed by the shape memory polymer andconverted into heat. The shape memory polymer will change shape whenheated above a transition temperature. When light from the diffusingchamber is absorbed in the SMP the polymer is heated and the proximalend relaxes to its primary shape. The primary shape of the SMP is formedby heating the SMP above its melting temperature as in extrusion ormolding processes. The SMP can be made by mold injection under vacuum.The mold used is a three part mold. The mold includes one male and twofemale sections. It is understood that the optical fiber 17 anddiffusing chamber 18 are part of the shape memory polymer (SMP) actuatorsystem 14 and these details will not be described in connection withadditional embodiments of the present invention.

[0070] Referring again to the drawings, FIG. 6 is a schematicillustration showing a closed SMP actuator in its pre-expanded shape foran embodiment of the present invention. One issue with creating aworking device is the method of collapsing the SMP such that it fills aminimum volume. In this embodiment, the closed design and the methodcreating the closed state are linked.

[0071] The SMP 23 was sliced along its length and then the SMP was woundaround the diffusing chamber 24. In order to create the loaded state, atube approximately twice the diameter of the fiber was pushed over theSMP 23 and simultaneously turned. This process was carried out in heatedwater that kept the SMP 23 above its transition temperature, Tg. The SMP23 was heated using 1 Watt from a 800 nm diode laser coupled into a 1mm-core optical fiber. Prior to the laser being turned on, the SMP 23 isclosed around the diffusing chamber 24. After the laser is turned on,light energy transmitted through the optical fiber 25 will cause the SMP23 to open.

[0072] The closed SMP 23 of the present invention can containthrombolytic agents 26 that are released at the blockage site when theSMP actuator is opened. These agents can be liquid 26 held in the SMP 23or coatings on the inner side 27 of the SMP 23 material. The closedstate is shown in FIG. 6. The SMP 23 can be meshed or otherwise haveholes in it such that as a blockage volume fills the opened SMP 23, thefluid 26 inside is displaced through the mesh. The expanded SMP 23 canform a chamber to collect more blockage material.

[0073] Referring now to FIGS. 7, 8, 9, and 10, embodiments of the SMPactuator system of the present invention are illustrated. The SMPactuator system is generally designated by the reference numeral 28. Asshown in FIG. 7, the actuator 29 is used in conjunction with a guidetube (catheter) 30 where the expanded actuator 29 with blockage materialmay be either locked around the guide tube 30, with the whole assemblyretracted from the lumen, or pulled through the guide tube 30. Acentering device 31 is added to the optic fiber 32 just proximal to theSMP actuator 29. This centering device 31 assists in guiding theexpanded actuator 29 back into the guide tube 30 when the fiber opticcore 32 is retracted relative to guide tube 30.

[0074] As shown by the embodiment of FIG. 8, the guide tube 30 andexpanded actuator 29 are made such they can mechanically lock. Thislocking mechanism may be active as in the case of the distal tip 33 ofthe guide tube 30 being an SMP actuator itself. In this case, thelocking mechanism may also be constructed out of SMP material (e.g. asecond SMP that contracts around the expanded “umbrella” actuator). Asshown in FIG. 9, the guide tube (catheter) 30 may be flared at itsdistal tip to easily accept the expanded actuator 29. This enablescollapsing the SMP actuator 29.

[0075] The SMP actuator 29 of the present invention can containthrombolytic agents that are released at the blockage site when the SMPactuator 29 is opened. These agents can be liquid held in the SMP orcoatings on the inner side of the SMP material.

[0076] Dye may be added to the SMP. Since the light absorption in theSMP actuator 29 facilitates the conversion from optical to thermalenergies, the dye concentration may be adjusted so that the light isoptimally absorbed in the SMP actuator. Variations of the dyeconcentration can be used to control heating uniformity and efficiency.Parameters that can be used to control the absorption is dye type,concentration, z-axis (along the length of the fiber) dye gradient, thep-axis distribution (around the circumference of the SMP), and r-axis(through the thickness of the SMP) dye gradient. As shown in theembodiment of FIG. 10, the SMP actuator 29 and optical fiber 32 arecarried by a delivery catheter 30. The delivery catheter 30 is containedin a guide catheter 35.

[0077] The method of use of the actuator 29 is generally described asworking in conjunction with a tube that both delivers the actuator tothe blockage and works with the actuator to reshape or remove blockages.The basic design with the addition of a hollow balloon or centeringdevice 34 is shown in the embodiment of FIG. 10. If the whole assembly(guide tube and actuator) is to be utilized, then the method may employa mating between the tube and actuator as shown in the embodiment of inFIG. 8. Alternatively, the device may be optimally used if the guidetube remains in place while the actuator (and other devices) is removedthrough the tube. Features that enable this are a flared distal tipshown in the embodiment of FIG. 9 and the centering device shown in FIG.7, that both may be SMP actuators in and of themselves. Devices caneither contain the clot remotely, i.e., at the site of the SMP umbrella,or by retracting it into a docking stand at the distal end of a deliveryor “tracker” catheter 30 shown in the embodiment of FIG. 10. Remotecapture is desired because the guide catheter is difficult, if notimpossible, to pass through the carotid sinus or bulb. The docking standcan be accomplished by either using an activatable SMP flaring devicesuch as shown in the embodiment of FIG. 9 or by using a hollowinflatable balloon 34 such as shown in the embodiment of FIG. 10. Alsonote that the balloon concept could be used provide a local cap or lidon the proximal end of the SMP umbrella clot catcher while alsoproviding a means to center the device upon retracting into the deliveryor “tracker” catheter 30.

[0078] Referring now to FIGS. 11 and 12, the use of a tether 41 to closethe expanded SMP actuator 38 is shown. The proximal end of the SMP 39may be tethered such that tension on the tethers 41 results in thepartial and/or complete collapse of the SMP (e.g. Reversible actuation,as shown in FIGS. 11 and 12.) This tethering may be accomplished byusing connectors, similar to materials described above, that runparallel to the z-axis. The tethers may be actuated by attaching theirproximal end to a second tube 42 that may slide over the fiber optic 43.

[0079] Referring to FIGS. 13 and 14, other systems for collapsing theSMP actuator 38 can be employed. Cutting away axial sections 40 of thematerial 39 of the SMP actuator 38 would also result in a collapsedstate with a low cross-sectional area as show in FIGS. 13 and 14. Theresulting radial sections are then connected along their circumferenceby wires or thread that would make the expanded actuator look more likea basket than an umbrella. The connective material may be located atmultiple locations along the z-axis and may be attached to the SMP“petals” by adhesives, embedding or sandwiching the connections betweenthe SMP and another material (possibly SMP).

[0080] The collapsing of the SMP can be facilitated by a light source.The collapse of the SMP may be enhanced by turning the light source on.The heating of the SMP while employing a method for collapsing the SMP(such as tethers) and subsequently turning the light source off willresult in the SMP holding a second collapsed state. This may be used tocontain the blockage between the SMP and diffusing chamber as well asreducing the proximal SMP diameter, which makes retracting through theguide tube more practical. Similarly, if another means were used to openthe SMP, such as “pusher” rods instead of “pulling” tethers, then use oflight or other heating mechanism to soften the SMP during this processfollowed by removal of heat will result in the SMP hardening andmaintaining an open state. Other means of opening the softened umbrellacan be employed including fluidic means (such as gas or liquid flowingfrom the catheter toward the umbrella to force it into an open state)and electrostatic means (where similar charges on the umbrella andsupport (ie, fiber) repel one another.

[0081] In the case of medical applications of the device, the design maybe enhanced by integrating radio-opaque markers 44, 45, and 46 into theSMP as shown in the embodiments shown in FIGS. 15A, 15B, and 15C. Thesemarkers 44, 45, and 46 and their relative movement with respect to eachother can be used to determine the actuation state of the device (e.g.open or closed). The markers are imaged via fluoroscopy. A minimum ofthree markers placed symmetrically around the proximal edge of the SMP(e.g. 3 markers—120° separation, 4 markers—90° separation, etc.) wouldallow the two-dimensional fluoroscopy images to visualize the actuationof the device. FIG. 15B and FIG. 15C show an end view of the SMP 39 withthree markers 44 near the outer circumference of the umbrella section.FIG. 15B illustrates circular markers in the umbrella section while themarkers in FIG. 15C are arbitrarily shaped. These markers would beeither attached to or embedded in the SMP. Their minimal size isdictated by current fluoroscope resolution. Since medical catheterstypically have multiple radio-opaque markers, this device is likely tohave other marker rings along its length, including one near the distaltip of the device. The device may employ radio-opaque markers forlocating the distal and proximal ends of the SMP clot catcher as well asdetermining if the device is closed for insertion or open for clotentrapment. These radio-opaque markers would be accomplished bylocalized doping of the SMP with a radio-opaque metal such as platinumor other heavy, yet biocompatible element.

[0082] As shown in the embodiment of FIG. 16, the basic device may beenhanced by adding a diagnostic sensor 47 at the distal tip of theactuator. Since the method-of-use includes pushing the device through oraround a blockage, a sensor 47 on the distal tip allows for theinterrogation of the environment distal to the blockage. In medicalapplications, for example, this could include a diagnostic that wouldmeasure the viability of the distal vessel relative to reinstated bloodflow. Since reintroducing blood to necrotic tissue will result in apotentially worse medical condition, a sensor that would help determinethe health of the vessel wall would be extremely useful. The sensor maybe any type but is likely to be light based. The use of multiplewavelengths and wavelength-specific reflective coatings 47 b enable adevice to be built that keeps the heating wavelength(s) confined to thediffusing chamber and allows diagnostic wavelengths to pass to thedistal tip and back. Alternatively, the same wavelength(s) may be usedfor both actuating the SMP and interrogating the diagnostic. In thiscase, instrumentation techniques like heterodyne detection, interferenceor fluorescence may be useful in isolating the optical changes to thesensor at the distal tip. In the case of an optical sensor, a sensor 48can be attached, deposited or embedded in the distal end of the deviceas shown in FIG. 17.

[0083] As shown in the embodiment of FIG. 18, light is coupled directlyinto the SMP volume 49 a aimed at the umbrella section 49 b whereactuation is required. A shaped reflector 50 a shown in FIG. 18 will aimthe light uniformly into the SMP umbrella section 49 b and lightdelivery is maximized by reflective coatings 50 b on both the fibercircumference and the SMP. Reflective coatings 50B could exist on allexterior surfaces (making use of any variety of coating techniques)while the internal interface between the fiber end 51 and SMP remainsprotected from such reflective coating. It is possible to index-matchthe fiber end 51 with the SMP (possibly using an antireflection layer ifthe indices of refraction are very different), where this interfacesurface could also be shaped to enhance uniform illumination in theumbrella portion 49 b where it is doped with dye and thus minimize backreflection and maximize absorption. A dome or parabolic cap 50 c wouldlikely cover a sharp conical reflecting tip 50 a to prevent it fromdamaging or rupturing blood vessels during transport.

[0084] As shown in the embodiment of FIG. 19, multiple umbrellas 52 areused. The final umbrella would likely have the least porosity (orsmallest holes for fluid to pass through) to catch the smallerparticles. Multiple umbrellas are used to improve the probability ofcatching all the debris.

[0085] Referring now to FIG. 20, instead of having a guide tube fortrapping the blockage (before extraction) it is possible to make use ofan opposing SMP umbrella 53 to minimize the initial size of the deviceand maximize the maneuverability during insertion. The outer rim or edgeof the umbrella is strong in only one direction. One could also use theopposing umbrellas 53 and 54 to push back and forth to scrape materialoff of the walls in both directions and have the debris move into thevoid between them.

[0086] Opposing umbrellas 53 and 54 can be used to scrape the walls inboth directions and contain more of the debris. Ideally the opposingumbrella 53 (shown on the left in FIG. 20) can move and lock with themain umbrella. The opposing umbrella could ride on a separate sleevewith independent illumination means or an SMP device could cause thetranslation, eliminating the need for axial translations between thefiber and a sleeve or tube. The SMP method is illustrated in FIGS. 21and 22. Different wavelengths and filters or having different transitiontemperatures would enable independent control of the two SMP devices.The same or different wavelengths can be used with the two SMP devices55 and 56 shown (with the same or different transition temperatures) toactuate the umbrellas and interlock to enclosed the material that is tobe extracted.

[0087]FIG. 23 shows end views of the two umbrellas positioned adjacenteach other to illustrate how the teeth along the outer rim of the twoumbrellas interlock and provide improved scraping. Teeth 57 and 58 alongthe outer rim of the umbrella can make for easy interlocking and may bedesigned for improved scraping. FIG. 23 shows a triangular tooth design57. FIG. 24 shows the two umbrellas positioned together illustrating howthe teeth along the outer rim of the two umbrellas interlock. FIG. 24shows a rounded tooth design 58.

[0088]FIG. 25 shows a snap type locking method where the rim of one cone59 snaps into the rim of the other cone 60 to enclose the debris throughoptical actuation. The cones 59 and 60 are forced together by theexpanding sleeve 60 a and the rim of one cone 59 snaps into the othercone 60.

[0089] Another embodiment, shown in FIG. 26, includes a barbed design 61inside the umbrella. This will hook the obstruction and reduce thepossibility of its escape. The barbs 61 inside and along the rim help tohook and hold the debris.

[0090] Another embodiment, shown in FIGS. 27 and 28, includes an SMPclamp 62 utilized to hold the pre-opened umbrella 63 in its closedposition throughout transport. This allows for positive and negativeaxial translation of the device through the passageways without openingthe umbrella. The clamp 62 holds the umbrella 63 closed duringtransport. The clamp 62 is opened and the pre-opened umbrella 63 isallowed to move to its expanded state. An SMP is used to release theclamp 63.

[0091] Tethers were mentioned in the embodiments illustrated in FIGS. 11and 12. An undesired effect of tethers is illustrated in FIGS. 29 and 30where the tethers push the debris away. As illustrated in FIGS. 29 and30, these tethers would have to cut through or circumvent the blockageto be helpful. Failure to do so could actually eject the blockage.Another embodiment that includes a tether 64 is illustrated in FIG. 31.An extension section 65 a of the umbrella prevents the debris from beingejected as it closes down on the blockage when tether 64 is pulled.

[0092] Referring now to FIG. 32, a second SMP device 65 b could be useto close an opened umbrella. The second SMP 65 b could have a differenttransition temperature but for more independent control of the SMPs,different wavelengths or polarizations of light could be used inconjunction with filters or polarizers. In general, maintainingpolarization in fibers is problematic and control at the output end withpolarizers and electronically controlled retarders make the system evenmore complex. Using two different wavelengths to open then close theumbrella is illustrated in FIG. 32 where an elongating sleeve putspressure on the umbrella for closure. The second SMP device 65 b, shownhere as an elongating sleeve, puts pressure on the umbrella to close itaround the debris.

[0093] Bistability was mentioned in regards to using tethers to closethe umbrella. The device in FIG. 32 is bistable without tethers. If youheat both SMPs until they become soft, then depending on which coolsfirst decides the mechanical state they will end up in. For example,turn the umbrella actuating light off first and it cools first, pushingaway the sleeve and assuming an open umbrella shape. Turn off theclosure device light first and the closure device pushes on the umbrellato close it somewhat. Turn on the umbrella actuating light and now youcan completely close and encapsulate the now soft umbrella.

[0094] Referring now to FIG. 33 another embodiment of a system,generally designated by the reference numeral 70, for heating the SMP isshown. A vessel 71 contains a blockage 73. The blockage 73 could be ablood clot, plaque, other emboli, or other blockage. A support structure72 with a shape memory material actuator 74 on its distal end isinserted through or around the blockage 73. The shape memory materialactuator 73 is used to remove the blockage 73 from the vascular system.Actuation is achieved by heating the shape memory material 74.

[0095] The shape memory material can be heated using various systems.These systems include induced resistive heating by an external wavefield, such as by an associated magnetic or radio frequency (RF) source,external heating through electrical induction or electrothermal heating,with local or remote ultrasonics or other acoustic means of energytransfer, or by converting optical energy into thermal energy thatallows the stored energy in the shape memory material to be released. Anexternal energy source 75 transmits energy, in the form of waves 76, tothe SMP actuator 74. The external source 75 may produce heating by anexternal wave field, such as by an associated magnetic or radiofrequency (RF) source, or by remote ultrasonics or other acoustic meansof energy transfer. The energy is absorbed by the shape memory materialand converted into thermal energy that heats the shape memory materialabove its transition temperature and the shape memory material moves toits primary shape, resulting in mechanical actuation. When the shapememory material actuator 74 is drawn backward it results in the removalof the blockage 73 from the vessel 71.

[0096] While the invention may be susceptible to various modificationsand alternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

The invention claimed is:
 1. A method of manufacturing an actuator foracting upon a material in a vessel, comprising the steps of: processinga shape memory polymer material so that it will expand into a somewhatumbrella shape upon being activated, and operatively connecting saidshape memory polymer material to an optical fiber.
 2. The method ofmanufacturing an actuator for acting upon a material in a vessel ofclaim 1 wherein said step of processing a shape memory polymer materialso that it will expand into a somewhat umbrella shape upon beingactivated, includes, heating said shape memory polymer material aboveits melting temperature during processing.
 3. The method ofmanufacturing an actuator for acting upon a material in a vessel ofclaim 1 wherein said shape memory polymer material has a primary shapebefore being activated and said step of processing a shape memorypolymer material so that it will expand into a somewhat umbrella shapeupon being activated, includes, polymerizing said shape memory polymermaterial while in its primary shape.
 4. The method of manufacturing anactuator for acting upon a material in a vessel of claim 2 wherein saidshape memory polymer material possesses a glass transformationtemperature (T_(g)) above which the material enters a reversible glassyphase where it becomes soft and flexible and easy to reshape thematerial and will return to its primary shape if not subjected to unduepressure and once cooled below T_(g), the shape is frozen in place andthe material becomes hardened and will hold its shape until it isintentionally relaxed by heating the SMP above T_(g) again.